1. Field
Embodiments described herein relate generally to a semiconductor storage device such as a NAND flash memory having a boosting circuit.
2. Background Art
As mobile devices such as portable telephones have spread in recent years, memories used in these mobile devices are required to have lower current dissipation.
For example, NAND flash memories are widely used in these mobile devices. It is extremely important to reduce the operation current of the NAND flash memories.
On the other hand, in “read”, “write (program)” and “erase” which are basic operations of the NAND flash memories, various boosted voltages (voltages generated in the memory which are higher than the power supply voltage supplied to the memory) generated by a boosting circuit are used.
For securing the reliability, therefore, a plurality of boosting circuits which supply various voltages are needed. As a result, the current consumption of the NAND flash memory is increased.
In some conventional boosting circuits, boosting stages are caused to operate in superposition to make the output voltage high by shifting phases of enable signals.
In the conventional boosting circuits, however, dissipate currents of pumps in respective boosting stages are not studied.